Code B673, Cruise - Vacuum Solenoid Circuit Problem: Notes

Fig 1: Code B673, Cruise Vacuum Solenoid Circuit Problem

Fig 2: Code B673, Cruise Vacuum Solenoid Circuit

Fig 3: Code B673, Schematic

The cruise control vacuum solenoid receives a rapidly switched voltage signal from the BCM to control the amount of time the solenoid is energized. During the time the output is "HIGH", the solenoid is energized and vacuum is supplied to the servo.

Code B673 will set if the cruise is on, the brake is not depressed, and the BCM output is "HIGH" when it should be "LOW"; or "LOW" when it should be "HIGH". Under these conditions, the BCM will disable the cruise control until the BCM sees the proper output signal. These determinations are made on the circuitry internal to the BCM and may not affect the "HIGH" or "LOW" displayed during "Service Mode"; as they only indicate what the BCM wants the output signal at, not what it is actually at. An output display of "LOW" means circuit 402 should be de-energized (vacuum solenoid off) and an output display of "HIGH" means circuit 402 should be energized (vacuum solenoid on).

Circuit 402 will be "HIGH" when the solenoid is energized, as the BCM is providing voltage to the vent solenoid which has its own full-time ground. Circuit 402 will be "LOW" when the solenoid is de-energized, as the BCM takes away the voltage feed to the solenoid.

1. BCM output BO02 cycles the vacuum solenoid. The "HIGH" and "LOW" refer to the state of the voltage at the BCM.
2. Checks to see if fault is due to servo or circuit.
3. Checks to see if fault is due to open ground circuit or control circuit, including servo solenoid.
4. Checks to see if fault is shorted servo or control circuit. If the vacuum solenoid is shorted (below 25 ohms), BCM replacement will also be necessary.